Should I build plinths or screw spikes into cabinet?


I've got a great old pair of B&W DM640 floor standers, but I don't have the plinth and spike kit that were sold as an option back in the '90s.  Since I have been unable to track down a kit online or directly through B&W I am planning on building my own.

The speakers themselves were built without any isolation system on the base of the cabinet, and were set on top of adjustable "lugs" which were incorporated into the top of the optional wooden plinths.  Each plinth had four basic spikes mounted at the corners.  This sounds easy enough to replicate.

Does it make more sense to simply drill into the base of the cabinet and mount the spikes directly?  The tweeters are nearly at ear level, so I don't need to lift them much.  I am a little hesitant to make any permanent alteration to the speakers, however.  Any opinions or alternatives are welcomed!
guitared
The Townshend Seismic Pods or Bars suggested by infection are great, but not cheap. For as little as $75 for a pair of speakers you can try roller bearings.
Thanks everyone for the responses.

Jamnesta, I contacted soundocity.com last week, and their cheaper option (non-custom) still added up to about 40% what I paid for the speakers not long ago, so I'm still looking for a cheaper option.

Infection - Are these available in a cryo-treated option? Haha.

bdp24 - I'll do some research on that avenue.  I'm hoping to stay <$100.
Good luck Guitared, I'm sure you'll come up with something for your speakers that's cost effective. I have little experience outside of the spikes I was provided with my speakers, but your post brings up an interesting quandary. Couple to the floor with spikes or decouple from the floor via the Townsend or some other method as suggested by Infection & bdp24. I imagine that's been debated endlessly here and elsewhere.....
As your budget is ideally less than  $100 then obviously the Seismic Bars are out of the question! 

Perhaps you could fashion your own version...!